04 Coppa Header Pipes w/o Crossover

[joe camarda]

In an effort to ease accessability to the alternator cover I am going to eliminate the front crossover.

 

A friend of mine who builds race pipes for Ducatis has offered to build a set of header pipes for my 04 Coppa. He has suggested using two inch pipes with a flange.

 

By increasing the front header pipes to 2 inches will I need to do a Power Commander set up?

 

FWIW my 04 Coppa has a FbF crossover installed, which at some point will be replaced by a Mistral. I currently have the MG Ti ECU installed, and the MG Ti exhaust pieces behind the FBF crossover are two inches in diameter.

 

Any comments or suggestions would be appreciated.

[Guest ratchethack]

Joe, awhile back Todd Eagan at GuzziTech was offering "unbreakable" replacement headers for V11's. You might check with him to see if he's taking a list for another run, or maybe he has some left. You might also get some feedback by way of the dyno numbers he achieved with them. FWIW, I have a friend with an '04 LM who finally put a stop to his endless nightmare with the troublesome front crossover by having the headers welded shut. He noticed no changes whatsoever in engine performance and made no change to his PC III.

 

The stock headers are 1 3/4", or 45 mm OD. Now this is just me, but without comprehensive head flow work and porting, custom intake and exhaust re-design, I wouldn't throw a considerably larger diameter header pipe in the stock mix without expecting lots more than a hard requirement for a map change just to make it run well, let alone give any power advantages. It's one o' those countless cases where "bigger" ain't necessarily "better" in the real world. For road-going purposes with your setup, I'd expect the far greater probability of unrecoverable loss of power where you want it the most.

 

But then, that's just me.

[Mike Stewart]

Ratchet is correct on the outside diameter of the header pipes being 1 3/4 inch., the header pipes also have a very thick wall so your inside diameter will be quite less than off the shelf 1 3/4" exhaust tubing.

 

I have been doing some research on exhaust theories and I am amazed on the science behind it. Some say keep the header pipe ID the same as the exhaust port in the cylinder head. Others like to go larger on the header pipe to keep the speed of the exhaust gasses high. Two inch might be on the big side, but I would be interested in seeing a dyno shootout of the different diameter header pipes. I vote for Joe doing the shootout

 

Another thought, will a 2 inch header pipe fit between the exhaust studs?

 

Mike

[Guest ratchethack]

Mike, I think you'll find that header pipe diameters are generally reduced for greater exhaust gas flow speed, not enlarged, and vice-versa. IIRC, Honda was a leader in this type of engine design back in the early '60's with their racing engines. The higher speed exhaust gas is used to create an "extractor" effect at early opening of the exhaust valve by using the mass of higher-speed exhaust to create a "lower bottom" of the negative pressure wave in the header. Honda used a "dual wall" header for street bikes with relatively small ID inner wall headers, achieving relatively high speed exhaust gas flow, incorporated with heads, cams, valves, timing, etc etc., all designed to take optimal performance advantage of this concept. In the late '60's I had a 350 Honda twin that IIRC redlined at 11,500 RPM. It used this design, and was noted for relatively high output for its day when it was revved "up on the cam".

 

Somebody posted here recently about a HD motor with huge diameter pipes, shooting flames and making lots of noise, but putting out sub-mediocre dyno curves. I reckon if the objective is to ride a noisemaker that shoots flames (many seem to be impressed by this) one doesn't care much about mileage or what true engineers consider "performance". On the other hand, if "circus performance" and making a spectcle of oneself is the objective, a flame-shooting noisemaker is probably just the ticket.

[Skeeve]

In an effort to ease accessability to the alternator cover I am going to eliminate the front crossover.

 

A friend of mine who builds race pipes for Ducatis has offered to build a set of header pipes for my 04 Coppa. He has suggested using two inch pipes with a flange.

 

By increasing the front header pipes to 2 inches will I need to do a Power Commander set up?

 

Well, if you change the ex. pipe dia., you'll definitely need to adjust the fuel map!

 

BTW, the R.o.T. on ex. pipe diameters is no more than 115% of the valve area, iirc. Easy calcs w/ a single valve, the pi's get eaten , & you can just use the valve dia. So given a 39mm ex. valve, that would mean a 45mm or 1.77" ex. pipe... what do ya know! 1&3/4" is right on the money! Maybe Guzzi knew what they were about after all?

[joe camarda]

Not wishing to test anyone's theory re a 2 inch pipe, I just decided to have my friend lop-off the section of each header where it joins to the cross-over and weld in a matching 1 3/4 replacement piece.

 

It looks thusly

[Skeeve]

Not wishing to test anyone's theory re a 2 inch pipe, I just decided to have my friend lop-off the section of each header where it joins to the cross-over and weld in a matching 1 3/4 replacement piece.

 

A wise decision, weedhoppa!

 

Your Coppa doesn't have 2" exhaust valves, so 2" headers are a non-starter. I don't much care who's pipe you're smokin', the theories all point to pipes no more than 10% larger or smaller than the exhaust valve, from what I've seen.

 

Your new & improved pipes look O.K. Now get'em coated w/ ceramic and ride off into the sunset...